Derek, I ran into a similar problem about six years ago, where a 10-30VDC product for use on earth-moving equipment had its DC power protected by a Microsemi 1.5KE51CA-T bidirectional transient suppressor. Applying a single -1kV EN 61000-4-5 surge between power and ground would short out the transient suppressor with fancy fireworks and lots of smoke.
In the first page of the datasheet for the 1.5KE51CA-T http://www.microsemi.com/en/sites/default/files/SA4-15.pdf under Applications/Benefits is the comment: "Secondary lightning protection per IEC61000-4-5 with 2 Ohms source impedance: * Class 2: 1.5KE5.0A to 1.5KE24A or CA * Class 3: 1.5KE5.0 to 1.5KE12A or CA" Our fix was to solder a second 1.5KE51CA-T in anti-parallel with the first one, which got us through the immunity requirements of EN 61326:1997 with no more problems. Apparently these transient protectors are bidirectional but not symmetrical-- their breakdown voltages and surge capabilities are different in the forward and backward directions. John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, Master EMC Design Eng, SM IEEE dBi Corporation http://www.dbicorporation.com/ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
